JavaScript

Javascript has been used primarily for programming the web browser and also used on the server-side with Node. Main uses include adding interactive behavior to web pages, Creating web and mobile apps, Building web servers and developing server applications, game development, etc. 

This key competency includes Functions, Events, and Error Handling, Currying, Hoisting, Scope, Inheritance, among others. 

Key Competencies:

1. Functions, Events, and Error Handling - A function is a set of statements that take inputs, do some specific computation, and produces output. JavaScript's interaction with HTML is handled through events that occur when the user or the browser manipulates a page. When the page loads, it is called an event. When the user clicks a button, that click is an event. Other examples include events like pressing any key, closing a window, resizing a window, etc. Explore different events and how to use them in this key competency. Explore Syntax Errors, Runtime Errors, and Logical Errors, and best practices to handle them. 
2. Currying - Explore currying, a process in functional programming in which developers can transform a function with multiple arguments into a sequence of nesting functions.
3. Hoisting, Scope, Inheritance - Hoisting is a JavaScript mechanism where variables and function declarations are moved to the top of their scope before code execution. Scope determines the accessibility of variables, objects, and functions from different parts of the code. JavaScript Inheritance works with objects and prototypes. Learn and explore the usage of Hoisting, Scope, and Inheritance. 
4. Closures - Knowledge and usage of Closure
5. Modules and Namespaces - Learn and explore the usage of modules and namespaces